The hypothesis that the affinity restriction in IgM arises from its restriction to the expression of germ-line variable region genes is under study. This analysis includes the preparation of monoclonal IgG and IgM antibodies specific for the Dnp and lactose epitopes. The affinity of a large number of such hybridomas is measured by the methods of fluorescence quenching and equilibrium dialysis. In addition the VH regions of the IgM antibodies will be isolated and the amino acid sequences will be established for the third hypervariable region, the D segment and the J segment. The interactions with monovalent and divalent ligands of monoclonal antibody attached to liposomal membranes will be evaluated kinetically and thermodynamically. The antibody will be attached covalently to the membrane in an orientation that renders its combining sites accessible to solvent components. The dependence of the interaction on the membrane composition and structure will also be analyzed.